The Experts below are selected from a list of 309 Experts worldwide ranked by ideXlab platform
Philip C Singer - One of the best experts on this subject based on the ideXlab platform.
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Exposure to drinking water disinfection by-products and pregnancy loss
American Journal of Epidemiology, 2006Co-Authors: David A Savitz, Katherine E Hartmann, Howard S. Weinberg, Amy H. Herring, Philip C Singer, Christina MakarushkaAbstract:Previous research has suggested that exposure to elevated levels of drinking water disinfection by-products (DBPs) may cause pregnancy loss. In 2000-2004, the authors conducted a study in three US locations of varying DBP levels and evaluated 2,409 women in early pregnancy to assess their tap water DBP concentrations, water use, other risk factors, and pregnancy outcome. Tap water concentrations were measured in the distribution system weekly or biweekly. The authors considered DBP concentration and ingested amount and, for trihalomethanes only, bathing/showering and integrated exposure that included ingestion. On the basis of 258 pregnancy losses, they did not find an increased risk of pregnancy loss in relation to trihalomethane, Haloacetic Acid, or total organic halide concentrations; ingested amounts; or total exposure. In contrast to a previous study, pregnancy loss was not associated with high personal trihalomethane exposure (> or =75 micro g/liter and > or =5 glasses of water/day) (odds ratio = 1.1, 95% confidence interval: 0.7, 1.7). Sporadic elevations in risk were found across DBPs, most notably for ingested total organic halide (odds ratio = 1.5, 95% confidence interval: 1.0, 2.2 for the highest exposure quintile). These results provide some assurance that drinking water DBPs in the range commonly encountered in the United States do not affect fetal survival.
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bench scale testing of a magnetic ion exchange resin for removal of disinfection by product precursors
Water Research, 2005Co-Authors: Treavor H Boyer, Philip C SingerAbstract:Abstract The objective of this research was to compare enhanced coagulation with anion exchange for removal of disinfection by-product (DBP) precursors (i.e. natural organic matter (NOM) and bromide). Treatment with a magnetic ion exchange resin (MIEX®) was the primary focus of this study. Raw waters from four utilities in California were evaluated. The waters had low turbidity, low to moderate organic carbon concentrations, a wide range of alkalinities, and moderate to high bromide ion concentrations. The treated waters were compared based on removal of ultraviolet (UV) absorbance, dissolved organic carbon (DOC), trihalomethane formation potential (THMFP), and Haloacetic Acid formation potential (HAAFP). The results indicated that treatment with MIEX is more effective than coagulation at removing UV-absorbing substances and DOC. Treatment with MIEX and treatment with MIEX followed by coagulation yielded similar results, suggesting that coagulation of MIEX-treated water does not provide additional removal of organic carbon. MIEX treatment reduced the THMFP and HAAFP in all waters, and did so to a greater extent than coagulation. Treatment with MIEX was most effective in raw waters having a high specific UV absorbance and a low anionic strength. Following MIEX treatment, subsequent chlorination resulted in a shift to the more brominated THM and HAA species as compared to chlorination of the raw water. MIEX also removed bromide to varying degrees, depending on the raw water alkalinity and initial bromide ion concentration.
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Factors Influencing the Formation and Relative Distribution of Haloacetic Acids and Trihalomethanes in Drinking Water
Environmental Science & Technology, 2003Co-Authors: Lin Liang, Philip C SingerAbstract:Various water quality and treatment characteristics were evaluated under controlled chlorination conditions to determine their influences on the formation and distribution of nine Haloacetic Acids and four trihalomethanes in drinking water. Raw waters were sampled from five water utilities and were coagulated with alum and fractionated with XAD-8 resin. The resulting four fractionsraw and coagulated water and the hydrophobic and hydrophilic extractswere then chlorinated at pH 6 and 8 and held at 20 °C for various contact times. The results show that increasing pH from 6 to 8 increased trihalomethane formation but decreased triHaloacetic Acid formation, with little effect on diHaloacetic Acid formation. More trihalomethanes were formed than Haloacetic Acids at pH 8, while the reverse was true at pH 6. Hydrophobic fractions always gave higher Haloacetic Acid and trihalomethane formation potentials than their corresponding hydrophilic fractions, but hydrophilic carbon also played an important role in disinfe...
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enhanced coagulation using a magnetic ion exchange resin
Water Research, 2002Co-Authors: Philip C Singer, Katya BilykAbstract:The objective of this investigation was to examine the effectiveness of a magnetic ion exchange resin (MIEX) to enhance the coagulation of disinfection by-product precursors in nine surface waters, each representing a different element of the USEPA's 3 x 3 enhanced coagulation matrix. The effect of MIEX-pretreatment on the requisite alum dose needed for subsequent coagulation of turbidity was also evaluated. Enhanced coagulation with MIEX was found to be very effective for removing trihalomethane (THM) and Haloacetic Acid (HAA) precursors from the nine waters examined. THM and HAA formation potential was reduced by more than 60% in all of the waters studied; reductions approaching 90% were seen in the waters with the highest specific ultraviolet absorbance values. The residual total organic carbon concentration, ultraviolet absorbance, and THM and HAA formation potential were all substantially lower as a result of MIEX and alum treatment compared to alum coagulation alone. MIEX pre-treatment also lowered the coagulant demand of each of the waters substantially.
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effect of bromide ion on Haloacetic Acid speciation resulting from chlorination and chloramination of aquatic humic substances
Environmental Science & Technology, 1996Co-Authors: Gretchen A Cowman, Philip C SingerAbstract:The objective of this study was to investigate the effect of bromide ion on the distribution of Haloacetic Acid (HAA) species resulting from the chlorination and chloramination of waters containing aquatic humic substances. Aquatic humic substances were extracted from a surface water and a groundwater and were chlorinated and chloraminated under standard conditions at pH 8 and pH 6 in the presence of bromide concentrations ranging from 0 to 25 μM (0−2 mg/L). The treated waters were analyzed for all nine of the HAA species containing bromine and chlorine. Standards for bromodichloroacetic Acid and dibromochloroacetic Acid were not commercially available but were synthesized for use in this study. Bromochloro-, bromodichloro-, and dibromochloroacetic Acid were readily formed and constituted at least 10% of the total HAA concentration in waters containing as little as 1.2 μM (0.1 mg/L) bromide. The mixed bromochloro HAA species were major components of the total HAA concentration at bromide concentrations fo...
Anne K Camper - One of the best experts on this subject based on the ideXlab platform.
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detection and enumeration of Haloacetic Acid degrading bacteria in drinking water distribution systems using dehalogenase genes
Journal of Applied Microbiology, 2009Co-Authors: Lynne H Leach, Ping Zhang, Raymond M Hozalski, Anne K Camper, Timothy M LaparaAbstract:AIMS: To develop a PCR-based tracking method for the detection of a subset of bacteria in drinking water distribution systems capable of degrading Haloacetic Acids (HAAs). METHODS AND RESULTS: Published degenerate PCR primers were used to determine that 54% of tap water samples (7/13) were positive for a deh gene, indicating that drinking water distribution systems may harbour bacteria capable of HAA degradation. As the published primer sets were not sufficiently specific for quantitative PCR, new primers were designed to amplify dehII genes from selected indicator strains. The developed primer sets were effective in directly amplifying dehII genes from enriched consortia samples, and the DNA extracted from tap water provided that an additional nested PCR step for detection of the dehII gene was used. CONCLUSIONS: This study demonstrates that drinking water distribution systems harbour microbes capable of degrading HAAs. In addition, a quantitative PCR method was developed to detect and quantify dehII genes in drinking water systems. SIGNIFICANCE AND IMPACT OF THE STUDY: The development of a technique to rapidly screen for the presence of dehalogenase genes in drinking water distribution systems could help water utilities determine if HAA biodegradation is occurring in the distribution system.
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isolation and characterization of Haloacetic Acid degrading afipia spp from drinking water
Fems Microbiology Letters, 2009Co-Authors: Ping Zhang, Raymond M Hozalski, Lynne H Leach, Anne K Camper, Emma H Goslan, Simon A Parsons, Timothy M LaparaAbstract:Haloacetic Acids are a class of disinfection byproducts formed during the chlorination and chloramination of drinking water that have been linked to several human health risks. In this study, we isolated numerous strains of Haloacetic Acid-degrading Afipia spp. from tap water, the wall of a water distribution pipe, and a granular activated carbon filter treating prechlorinated water. These Afipia spp. harbored two phylogenetically distinct groups of α-halocarboxylic Acid dehalogenase genes that clustered with genes previously detected only by cultivation-independent methods or were novel and did not conclusively cluster with the previously defined phylogenetic subdivisions of these genes. Four of these Afipia spp. simultaneously harbored both the known classes of α-halocarboxylic Acid dehalogenase genes (dehI and dehII), which is potentially of importance because these bacteria were also capable of biodegrading the greatest number of different Haloacetic Acids. Our results suggest that Afipia spp. have a beneficial role in suppressing the concentrations of Haloacetic Acids in tap water, which contrasts the historical (albeit erroneous) association of Afipia sp. (specifically Afipia felis) as the causative agent of cat scratch disease.
Simon A Parsons - One of the best experts on this subject based on the ideXlab platform.
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change in Haloacetic Acid formation potential during uv and uv h2o2 treatment of model organic compounds
Chemosphere, 2013Co-Authors: H Sakai, Olivier Autin, Simon A ParsonsAbstract:Haloacetic Acids (HAAs) are disinfection by-products produced by the chlorination of organic matter, including amino Acids. Advanced oxidation processes are expected to be effective for the destruction of HAA precursors; however, recent studies have reported the possible failure of these processes to reduce HAA formation potential. This study examined HAA formation potential during the course of UV or UV/H2O2 treatment of three organic compounds: leucine, serine, and resorcinol. HAA formation potential decreased in the treatment of resorcinol, while the potential increased slightly in the treatment of serine and greatly increased for leucine. The chemical structure required for HAA formation was assumed to be produced during the course of UV/H2O2 treatment of leucine and serine. Also, H abstraction from the δ carbon was assumed to result from the initial degradation of leucine by the hydroxyl radical during the UV/H2O2 treatment. The hydroxyl radical may have further reacted with leucine moiety to shorten its carbon chain. This would have produced a chemical structure capable of forming HAA, thus increasing HAA formation potential.
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a critical review of trihalomethane and Haloacetic Acid formation from natural organic matter surrogates
Environmental Technology Reviews, 2012Co-Authors: Tom Bond, Emma H Goslan, Simon A Parsons, Bruce JeffersonAbstract:Disinfection by-products (DBPs) in drinking water, including trihalomethanes (THMs) and Haloacetic Acids (HAAs), arise from reactions of natural organic matter (NOM) with chlorine and other disinfectants. The objective of this review was to investigate relationships between the molecular properties of NOM surrogates and DBP formation using data collated for 185 compounds. While formation of THMs correlated strongly with chlorine substitution, no meaningful relationships existed between compound physicochemical properties and DBP formation. Thus non-empirical predictors of DBP formation are unlikely in natural waters. Activated aromatic compounds are well known to be reactive precursors; in addition DBP formation from β-dicarbonyl, amino Acid and carbohydrate precursors can be significant. Therefore effective DBP control strategies need to encompass both hydrophobic and hydrophilic NOM components, as well as consider data from NOM surrogates in the context of knowledge from representative treatment scenari...
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isolation and characterization of Haloacetic Acid degrading afipia spp from drinking water
Fems Microbiology Letters, 2009Co-Authors: Ping Zhang, Raymond M Hozalski, Lynne H Leach, Anne K Camper, Emma H Goslan, Simon A Parsons, Timothy M LaparaAbstract:Haloacetic Acids are a class of disinfection byproducts formed during the chlorination and chloramination of drinking water that have been linked to several human health risks. In this study, we isolated numerous strains of Haloacetic Acid-degrading Afipia spp. from tap water, the wall of a water distribution pipe, and a granular activated carbon filter treating prechlorinated water. These Afipia spp. harbored two phylogenetically distinct groups of α-halocarboxylic Acid dehalogenase genes that clustered with genes previously detected only by cultivation-independent methods or were novel and did not conclusively cluster with the previously defined phylogenetic subdivisions of these genes. Four of these Afipia spp. simultaneously harbored both the known classes of α-halocarboxylic Acid dehalogenase genes (dehI and dehII), which is potentially of importance because these bacteria were also capable of biodegrading the greatest number of different Haloacetic Acids. Our results suggest that Afipia spp. have a beneficial role in suppressing the concentrations of Haloacetic Acids in tap water, which contrasts the historical (albeit erroneous) association of Afipia sp. (specifically Afipia felis) as the causative agent of cat scratch disease.
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parameters affecting Haloacetic Acid and trihalomethane concentrations in treated uk drinking waters
ACS symposium series, 2008Co-Authors: Cynthia M M Bougeard, Emma H Goslan, Imran H S Janmohamed, Bruce Jefferson, Jonathan S Watson, Geraint Morgan, Simon A ParsonsAbstract:Since their discovery, disinfection by-products (DBPs) have become one of the major driving forces in drinking water regulations, research and water utility operations throughout the world. The list of DBPs that can occur in treated drinking waters has grown from a few trihalomethanes to a long list of halogenated and non-halogenated organic or inorganic compounds. This list is expected to continue to grow as the analytical techniques are improved, as more information on their toxicity is developed, and as more occurrence studies are conducted. This book documents the latest DBP research findings, including emerging issues and state-of-the-art studies. Specifically, papers on the occurrence, formation, control, and health effects of emerging (unregulated) halogenated (e.g., brominated) and nonhalogenated (e.g., nitrosamines) DBPs (e.g., emerging nitrogenous vs. regulated carbonaceous DBPs) are presented. In addition to the characterization and reactivity of natural organic matter to form DBPs, new studies on algal organic matter and treated wastewater as sources of DBPs and their precursors are discussed.
S E George - One of the best experts on this subject based on the ideXlab platform.
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metabolism microflora effects and genotoxicity in Haloacetic Acid treated cultures of rat cecal microbiota
Toxicological Sciences, 2001Co-Authors: Gail M Nelson, Adam Swank, Lance R Brooks, K C Bailey, S E GeorgeAbstract:: Haloacetic Acids are by-products of drinking water disinfection. Several compounds in this class are genotoxic and have been identified as rodent hepatocarcinogens. Enzymes produced by the normal intestinal bacteria can transform some promutagens and procarcinogens to their biologically active forms. The present study was designed to investigate the influence of the cecal microbiota on the mutagenicity of Haloacetic Acids, and to look at changes in the microbiota populations and enzyme activities associated with exposure to Haloacetic Acids. PYG medium containing 1 mg/ml of monochloroacetic (MCA), monobromoacetic (MBA), dichloroacetic (DCA), dibromoacetic (DBA), trichloroacetic (TCA), tribromoacetic (TBA), or bromochloroacetic (BCA) Acid was inoculated with rat cecal homogenate and incubated anaerobically at 37 degrees C. Growth curves were performed with enumeration of the microflora populations on selective media. Mutagenicity in a Salmonella microsuspension bioassay was determined after incubation for various lengths of time, with or without the cecal microbiota. At 15 h of incubation, enzyme assays determined the activities for beta-glucuronidase, beta-galactosidase, beta-glucosidase, azoreductase, nitroreductase, dechlorinase, and dehydrochlorinase. The Haloacetic Acids, with the exception of BCA, were toxic to the cecal microbiota, and especially to the enterococci. DBA, TBA, and BCA were mutagenic in the microsuspension assay, but the presence of the intestinal flora did not significantly alter the mutagenicity. BCA increased the activities of several enzymes, and therefore has the potential to affect the biotransformation of co-exposed compounds.
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Metabolism, Microflora Effects, and Genotoxicity in Haloacetic Acid-Treated Cultures of Rat Cecal Microbiota
Toxicological Sciences, 2001Co-Authors: Gail M Nelson, Adam Swank, Lance R Brooks, K C Bailey, S E GeorgeAbstract:Haloacetic Acids are by-products of drinking water disinfection. Several compounds in this class are genotoxic and have been identified as rodent hepatocarcinogens. Enzymes produced by the normal intestinal bacteria can transform some promutagens and procarcinogens to their biologically active forms. The present study was designed to investigate the influence of the cecal microbiota on the mutagenicity of Haloacetic Acids, and to look at changes in the microbiota populations and enzyme activities associated with exposure to Haloacetic Acids. PYG medium containing 1 mg/ml of monochloroacetic (MCA), monobromoacetic (MBA), dichloroacetic (DCA), dibromoacetic (DBA), trichloroacetic (TCA), tribromoacetic (TBA), or bromochloroacetic (BCA) Acid was inoculated with rat cecal homogenate and incubated anaerobically at 37°C. Growth curves were performed with enumeration of the microflora populations on selective media. Mutagenicity in a Salmonella microsuspension bioassay was determined after incubation for various lengths of time, with or without the cecal microbiota. At 15 h of incubation, enzyme assays determined the activities for b-glucuronidase, b-galactosidase, b-glucosidase, azoreductase, nitroreductase, dechlorinase, and dehydrochlorinase. The Haloacetic Acids, with the exception of BCA, were toxic to the cecal microbiota, and especially to the enterococci. DBA, TBA, and BCA were mutagenic in the microsuspension assay, but the presence of the intestinal flora did not significantly alter the mutagenicity. BCA increased the activities of several enzymes, and therefore has the potential to affect the biotransformation of co-exposed compounds.
Michael Jacob Plewa - One of the best experts on this subject based on the ideXlab platform.
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Haloacetic Acid Water Disinfection Byproducts Affect Pyruvate Dehydrogenase Activity and Disrupt Cellular Metabolism
Environmental Science & Technology, 2018Co-Authors: Azra Dad, Elizabeth D. Wagner, Clara H. Jeong, Michael Jacob PlewaAbstract:The disinfection of drinking water has been a major public health achievement. However, Haloacetic Acids (HAAs), generated as by-products of water disinfection, are cytotoxic, genotoxic, mutagenic, carcinogenic and teratogenic. Previous studies of monoHAA-induced genotoxicity and cell stress demonstrated that the toxicity was due to inhibition of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) leading to disruption of cellular metabolism and energy homeostasis. DiHAAs and triHAAs are also produced during water disinfection, and whether they share mechanisms of action with monoHAAs is unknown. In this study, we evaluated the effects of mono-, di-, and tri-HAAs on cellular GAPDH enzyme kinetics, cellular ATP levels, and pyruvate dehydrogenase complex (PDC) activity. Here, treatments conducted in Chinese hamster ovary (CHO) cells revealed differences among mono-, di-, and triHAA in their molecular targets. The monoHAAs, iodoacedic Acid and bromoacetic Acid, were the strongest inhibitors of GAPDH and greatly...
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in vitro cytotoxicity and adaptive stress responses to selected Haloacetic Acid and halobenzoquinone water disinfection byproducts
Chemical Research in Toxicology, 2015Co-Authors: Erik Prochazka, Michael Jacob Plewa, Beate I Escher, Frederic D L LeuschAbstract:The process of disinfecting drinking water inadvertently leads to the formation of numerous disinfection byproducts (DBPs). Some of these are mutagenic, genotoxic, teratogenic, and cytotoxic, as well as potentially carcinogenic both in vivo and in vitro. We investigated the in vitro biological activity of five DBPs: three monoHaloacetic Acids (monoHAAs) [chloroacetic Acid (CAA), bromoacetic Acid (BAA), and iodoacetic Acid (IAA)] and two novel halobenzoquinones (HBQs) [2,6-dichloro-p-benzoquinone (DCBQ) and 2,6-dibromo-p-benzoquinone]. We focused particularly on cytotoxicity and induction of two adaptive stress response pathways: the oxidative stress responsive Nrf2/ARE and DNA-damage responsive p53 pathways. All five DBPs were cytotoxic to the Caco-2 cell line after a 4 h exposure, and all DBPs induced both of the adaptive stress response pathways, Nrf2/ARE and p53, in the micromolar range, as measured by two β-lactamase-based reporter gene assays. The decreasing order of potency for all three endpoints f...
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Pyruvate remediation of cell stress and genotoxicity induced by Haloacetic Acid drinking water disinfection by-products.
Environmental and Molecular Mutagenesis, 2013Co-Authors: Azra Dad, Elizabeth D. Wagner, Clara H. Jeong, Justin A. Pals, Michael Jacob PlewaAbstract:MonoHaloacetic Acids (monoHAAs) are a major class of drinking water disinfection by-products (DBPs) and are cytotoxic, genotoxic, mutagenic, and teratogenic. We propose a model of toxic action based on monoHAA-mediated inhibition of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) as a target cytosolic enzyme. This model predicts that GAPDH inhibition by the monoHAAs will lead to a severe reduction of cellular ATP levels and repress the generation of pyruvate. A loss of pyruvate will lead to mitochondrial stress and genomic DNA damage. We found a concentration-dependent reduction of ATP in Chinese hamster ovary cells after monoHAA treatment. ATP reduction per pmol monoHAA followed the pattern of iodoacetic Acid (IAA) > bromoacetic Acid (BAA) >> chloroacetic Acid (CAA), which is the pattern of potency observed with many toxicological endpoints. Exogenous supplementation with pyruvate enhanced ATP levels and attenuated monoHAA-induced genomic DNA damage as measured with single cell gel electrophoresis. These data were highly correlated with the SN2 alkylating potentials of the monoHAAs and with the induction of toxicity. The results from this study strongly support the hypothesis that GAPDH inhibition and the possible subsequent generation of reactive oxygen species is linked with the cytotoxicity, genotoxicity, teratogenicity, and neurotoxicity of these DBPs.
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Biological mechanism for the toxicity of Haloacetic Acid drinking water disinfection byproducts.
Environmental Science & Technology, 2011Co-Authors: Justin A. Pals, Elizabeth D. Wagner, Justin K. Ang, Michael Jacob PlewaAbstract:The halogenated acetic Acids are a major class of drinking water disinfection byproducts (DBPs) with five Haloacetic Acids regulated by the U.S. EPA. These agents are cytotoxic, genotoxic, mutagenic, and teratogenic. The decreasing toxicity rank order of the monohalogenated acetic Acids (monoHAAs) is iodo- > bromo- ≫ chloroacetic Acid. We present data that the monoHAAs inhibit glyceraldehyde-3-phosphate dehydrogenase (GAPDH) activity in a concentration-dependent manner with the same rank order as above. The rate of inhibition of GAPDH and the toxic potency of the monoHAAs are highly correlated with their alkylating potential and the propensity of the halogen leaving group. This strong association between GAPDH inhibition and the monoHAA toxic potency supports a comprehensive mechanism for the adverse biological effects by this widely occurring class of regulated DBPs.
